Dense wavelength division multiplexing, DWDM, technology has widespread application in metro networks. It can offer advantages in term of bandwidth capabilities and scalability also in mobile backhaul and radio access networks, particularly because demand for broadband services and bandwidth, especially peak rate and cell load, is increasing with time. DWDM permits ultra-broad dedicated bandwidth and very low latency for each or a cluster of radio base stations. A typical mobile backhaul network comprises two aggregation stages, namely low radio access network, LRAN, and high radio access network, HRAN, characterized respectively by hundreds and thousands of connections, using Layer 2/3 switches.
Optical switches can be used in place of electric switches to offer energy saving and increased bandwidth. Current solutions for optical switches are typically based on Wavelength selective devices (WSS) which are costly and bulky devices based on complex free space optics. This has prevented the introduction of photonic switching in access and mobile backhaul networks where the capacities involved are lower, ranging from 10s up to 100s Gbps, where cost and footprint are critical characteristics and where the required performances are lower than in WSS devices due a lower number of nodes traversed and to shorter inter-nodal path lengths. E. J. Klein et al “Densely integrated microring resonator based photonic devices for use in access networks”, Optics Express, pages 10346-10355, vol. 15, no. 16, 6 Aug. 2007, reports two reconfigurable optical add-drop multiplexers and a 1×4×4 reconfigurable wavelength-router based on thermally tunable vertically coupled micro-ring resonators fabricated in Si3N4/SiO2.